Spherometer Disc Type PSAW |
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| Spherometer Disc Type PSAW
(1239 A) |
It consists of a small metal frame, supported by three legs fixed at the corners of an equilateral triangle. A screw of fine pitch passes through the center of the metal frame. The screw forms the fourth leg. The main scale (or pitch scale) is marked in a metal strip fixed at right angles to the frame. This scale is marked in millimeters with zero mark at the center (10-0-10 mm). A circular scale is fixed to the screw head. It carries a circular scale divided in 100 equal parts (In some cases it is divided into 50 equal parts). The edge of strip is used also as a reference line fro taking the circular scale reading. The disc & scales are brass lacquered & legs are made of steel black painted.
1) 1/100
2) 1/200
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